The present invention relates to a selective ink-jet printing device for alphanumeric serial-parallel printing and/or for printing of facsimile type, comprising a plurality of containers for inks of different colours and a plurality of nozzles connected to the containers. The invention also relates to the types of ink which are adapted to permit ink-jet printing in several colours, both by super-imposition and by the bringing near of colours, and to a method of preparation of such inks.
Devices for printing in several colours are known wherein the nozzles are borne by a single structure and are connected to different ink reservoirs. In one known device, the droplets of ink are expelled from the nozzles by means of pressure impulses generated by piezoelectric elements. The droplets of ink turn out relatively heavy, however, creating both problems of drying and superimposition of colours and problems of blocking of the nozzles, especially in the case of little used colours.